JP3884561B2 - Plasma cleaning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma surface treatment apparatus that performs various treatments using plasma such as film formation, etching, and cleaning on the surface of a semiconductor chip, small mechanical electrical component, and the like.
[0002]
[Prior art]
Plasma is used to deposit and stack conductor layers and insulating layers on the surface of semiconductor substrates, small mechanical electrical components, optical plastic components, etc., and conversely to etch the surfaces of semiconductor substrates and laminates. Processing is now very widespread. In recent years, a dry cleaning process using plasma has been widely used for cleaning for removing dirt on the surface of a substrate or the like instead of a conventional wet process using chlorofluorocarbon.
[0003]
The principle of surface treatment with plasma is explained as follows. That is, a pair of electrodes consisting of an electrode (RF electrode) connected to a high-frequency power source (RF power source) and a grounded electrode (ground electrode) are arranged in a sealable reaction chamber, and air is sufficiently removed from the reaction chamber. To do. In this state, when power is supplied to the RF electrode at a high frequency (usually 13.56 MHz) by starting the RF power supply while supplying the reaction gas (Ar, O _2, etc.) into the reaction chamber, Low temperature plasma (cations and electrons) and radical species are generated. Here, due to the difference in mobility between ions and electrons, the electrons are collected by the RF electrode and the RF electrode is relatively negatively charged (self-bias), while radical species and cations are easily It moves in the plasma without being collected. When an object to be processed is arranged in the plasma, radical species or cations that move in the plasma collide with or come into contact with the surface of the object to be processed. Thus, the surface treatment (cleaning, etching, film formation, etc.) of the object to be processed is performed.
[0004]
There are several forms (modes) of the plasma processing method, and two of them, the reactive ion etching (RIE) mode and the plasma etching (PE) mode, will be described with reference to FIGS. 6 and 7, reference numeral 61 denotes an RF power source, reference numeral 62 denotes an RF electrode, reference numeral 63 denotes a ground electrode, reference numeral 64 denotes a capacitor, and reference numeral 65 denotes an object to be processed.
[0005]
In the PE mode, as shown in FIG. 6, plasma is generated in a state where the workpiece 65 is placed on the ground electrode 63 formed in a plate shape. Then, since the positive ions are attracted by the negatively charged RF electrode 62, radical species mainly collide with or come into contact with the surface of the workpiece 65. On the other hand, in the RIE mode, as shown in FIG. 7, plasma is generated between the electrodes as described above in a state where the workpiece 65 is placed on the RF electrode 62 formed in a plate shape. Then, cations attracted by the negatively charged RF electrode 62 collide with the surface of the workpiece 65. Compared to the RIE mode and the PE mode, the RIE mode is suitable for physical and high-speed surface treatment by ion bombardment. On the other hand, the PE mode is suitable for chemical and mild surface treatment with radical species at a low speed.
[0006]
[Problems to be solved by the invention]
As shown in FIG. 6 or FIG. 7, the plasma surface treatment apparatus configured to place an object to be processed on the electrode plate has a small number of objects to be processed that can be placed on the electrode plate at one time. For this reason, in order to process a large number of objects to be processed, a series of steps of loading the objects to be processed, evacuating the reaction chamber, plasma processing, opening the reaction chamber, and unloading the objects to be processed must be repeated. However, it takes time and the productivity is remarkably lowered.
[0007]
Of course, if a shelf (hereinafter referred to as a magazine) including a plurality of shelf plates arranged hierarchically is used, a large number of objects to be processed can be stored in the reaction chamber and exposed to plasma at a time. However, especially when processing in the RIE mode, the cation density in the space near the object to be processed depends on the distance between the object to be processed and the RF electrode. There is a problem of coming. In addition, the conventional magazine has a metal outer wall, and this outer wall hinders the flow of plasma molecules into the magazine.
[0008]
The present invention has been made in order to solve such problems. The object of the present invention is to provide space efficiency and to treat a large number of objects to be treated at once and uniformly, as well as reaction. It is an object of the present invention to provide a plasma surface treatment apparatus capable of easily and in a short time setting a workpiece to be processed and taking out the workpiece from a reaction chamber.
[0009]
[Means for Solving the Problems]
The plasma surface treatment apparatus according to the present invention, which has been made to solve the above problems,
a) High frequency power supply,
b) a magazine including a plurality of shelves made of a conductive material and an outer frame that hierarchically supports the shelves;
c) a reaction chamber that can be sealed with the magazine stored therein;
d) electrical connection means for electrically connecting the shelf of the magazine housed in the reaction chamber to the high frequency power source;
e) a ground electrode installed so as to cover the ceiling and side surfaces of the reaction chamber;
It is characterized by providing.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The magazine used in the plasma surface treatment apparatus according to the present invention has a structure in which a plurality of shelf boards for placing an object to be processed are hierarchically supported by an outer frame. The magazine shelf is made of a conductive material. After the magazine is stored in the reaction chamber, all the shelves are connected to a high frequency power source by electrical connection means. When high frequency power is supplied to the magazine housed in the reaction chamber in this way, plasma is generated in the space between the shelves. The surface of the object to be processed placed on each shelf board is processed by this plasma.
[0011]
The electrical connection means, for example, creates the outer frame from a conductive material, arranges an electrode connected to the high-frequency power source on the floor surface of the reaction chamber, and places the magazine at a predetermined position in the reaction chamber. What is necessary is just to set it as the structure that the said outer frame and the said electrode will be electrically connected if mounted.
[0012]
As a preferred form of the magazine, there may be mentioned one in which the outer frame is formed in a rectangular parallelepiped shape and an opening for introducing external plasma into the inside is provided on the side surface. Such a magazine is advantageous in that it is easy to create and that plasma generated outside the magazine easily flows into the inside through the opening.
[0013]
In the plasma surface treatment apparatus according to the present invention, the magazine is preferably removable from the reaction chamber. Such a plasma surface treatment apparatus can handle not only a large number of small objects to be processed but also a large object to be processed by removing the magazine from the reaction chamber. In addition, when the processing steps for the object to be processed include a plurality of processes including the plasma surface treatment, it is possible to move from one process to the next process while the object to be processed is placed on the magazine. The troublesome work of individually moving the workpieces becomes unnecessary, and the work efficiency is increased.
[0014]
In the plasma surface treatment apparatus according to the present invention, it is preferable that the shelf board is removable from the outer frame. In this way, it becomes easy to place the workpiece on the shelf board and to remove it from the shelf board. Moreover, this plasma surface treatment apparatus can cope with processing of a larger object by removing all the shelf boards.
[0015]
【The invention's effect】
According to the plasma surface treatment apparatus according to the present invention as described above, since a large number of objects to be processed can be collectively processed, the processing efficiency is increased. In addition, when the magazine can be taken out from the reaction chamber and / or when the shelf plate can be removed from the magazine, the processing object can be carried into the reaction chamber or the processing object can be carried out from the reaction chamber. The plasma surface treatment apparatus of the present invention can be used not only for easy processing but also for processing larger workpieces.
[0016]
【Example】
FIG. 1 is a perspective view showing a plasma surface treatment apparatus 10 according to an embodiment of the present invention. The plasma surface treatment apparatus 10 includes a treatment unit 11 having a rectangular parallelepiped shape and a control unit 12 provided in the same casing. A reaction chamber 13 is provided inside the processing unit 11. An RF electrode 14 is embedded in the floor surface of the reaction chamber 13, and a magazine 15 described later is placed thereon. When the door 16 provided on the front surface of the processing unit 11 is opened as shown in the figure, the magazine 15 can be taken out from the reaction chamber 13. When the door 16 is closed, the reaction chamber 13 becomes an airtight closed space. On the other hand, the control unit 12 includes an RF power source for supplying high-frequency power for plasma generation (usually 13.56 MHz) to the RF electrode 14 in the reaction chamber 13, a vacuum pump for removing air from the reaction chamber 13, A gas supply unit for sending a reaction gas (for example, Ar) supplied from a gas source (not shown) into the reaction chamber 13 and a control circuit for controlling the operation of the entire apparatus are housed.
[0017]
FIG. 2 is a perspective view of the magazine 15. The magazine 15 includes a rectangular parallelepiped outer frame 151 having a structure in which a top plate 157 is supported by four columns 156 erected at four corners of a rectangular bottom plate 155 and five shelf plates 152. Between the pair of support columns 156 and 156 constituting the right side surface or the left side surface of the outer frame 151, five stages of rails 153 for supporting the shelf plate 152 are provided on each side surface. The shelf board 152 is slidably supported by a pair of rails 153 and 153 at the same height. Although not shown, it is preferable to provide a fixing means (for example, a screw or a clamper) for fixing the shelf board 152 at a predetermined position on the rail 153 at an appropriate position on the outer frame 151 or the rail 153. The outer frame 151 and the shelf board 152 are made of a conductive material such as stainless steel (SUS) or aluminum.
[0018]
FIG. 3 is a diagram showing the configuration of the processing unit 11 and the configuration of the electrical system related to the plasma surface treatment. In the reaction chamber 13, a ground electrode 20 is provided so as to cover the ceiling surface and side surfaces (except for the side to which the door 16 of FIG. 1 is attached). The RF electrode 14 embedded in the floor of the reaction chamber 13 is connected to an RF power source 61 via a capacitor 64. The ground electrode 20 and the RF electrode 14 are insulated by an insulating member 21. On the other hand, since the magazine 15 is in contact with the RF electrode 14 at the bottom plate 155, electrical conduction is possible between them. In order to make electrical conduction more reliable, for example, connection terminals may be provided on the upper surface of the RF electrode 14 and the bottom surface of the bottom plate 155. A workpiece 22 is placed on each shelf 152 of the magazine 15. Further, the processing unit 11 is provided with a gas inlet 111 for supplying a reaction gas into the reaction chamber 13 and a gas outlet 112 for discharging the gas in the reaction chamber 13 to the outside.
[0019]
In the processing unit 11 as described above, in order to perform the surface treatment of the workpiece 22, the air in the reaction chamber 13 is removed from the gas outlet 112 and then the reaction gas is supplied from the gas inlet 111 into the reaction chamber 13. Meanwhile, high frequency power is supplied from the RF power source 61 to the RF electrode 14. Then, the electric power is supplied from the RF electrode 14 to each shelf plate 152 through the bottom plate 155, the support column 156, and the rail 153. That is, all the shelves 152 function as electrodes that ionize gas in the same manner as the RF electrode 14. And all the to-be-processed objects 22 mounted in the shelf board 152 receive the plasma surface treatment of RIE mode simultaneously. Thus, the surface treatment of a plurality of objects to be processed is performed at once.
[0020]
Further, since the outer frame 151 of the magazine 15 does not have a side wall surface, the plasma generated between the magazine 15 and the RF electrode 14 easily flows into the magazine 15. Thereby, the processing efficiency is further enhanced.
[0021]
Various parameters can be considered for effectively generating plasma discharge in the reaction chamber 13. Regarding the dimensions and shapes of the reaction chamber 13 and the magazine 15, the outer surface of the magazine 15 and the reaction chamber 13 can be considered. The distance between the inner wall (that is, the surface of the ground electrode 20) (hereinafter referred to as A dimension) and the distance between each shelf 152 (or the distance between the ceiling of the magazine 15 and the uppermost shelf 152). Hereinafter, the dimension B) affects the generation of plasma discharge. FIG. 4 is a graph showing the experimental results of examining the relationship between the setting of the A and B dimensions and the occurrence of plasma discharge. This experiment was performed under the conditions that the gas pressure in the reaction chamber 13 was 89 mTorr and the output of the RF power source was 50 W.
[0022]
Referring to the graph of FIG. 4, the dischargeable region is included in the range where the B dimension is 20 mm or more. From this, when the gas pressure and the power supply output are given, it is considered that the minimum value of the B dimension capable of generating the plasma discharge is determined accordingly. On the other hand, when the value of dimension B is increased, the number of shelf boards 152 that can be mounted on the magazine 15 is reduced accordingly, and space utilization efficiency is reduced. Considering the above, when the gas pressure and the power output are predetermined, it is preferable to set the B dimension to the minimum value.
[0023]
As mentioned above, although one Example of the plasma surface treatment apparatus concerning this invention was described, it cannot be overemphasized that an Example is not restricted to said thing. For example, in the plasma surface treatment apparatus of FIG. 1, a user opens the door 16 and manually carries out the work to be carried into the reaction chamber 13 and the work to be carried out from the reaction chamber 13. Although it was assumed, if a device (hereinafter referred to as an automatic transfer device) that automatically carries in and out such a workpiece is further provided, the processing efficiency is further increased. An example of a processing unit suitable for a plasma surface processing apparatus provided with such an automatic transfer device will be described below with reference to FIG.
[0024]
The processing unit 11 </ b> A shown in FIG. 5 is divided into a lid portion 115 in which the ground electrode 20 is housed and a bottom portion 116 in which the RF electrode 14 is embedded. When the lid 115 is placed on the bottom 116 and the two are completely coupled by a predetermined fixing means, an airtight reaction chamber 13 is formed inside. The lid 115 is driven in the vertical direction by a lid driving mechanism (not shown). The operation of the lid driving mechanism driving the lid 115 is interlocked with the operation of carrying in / out the workpiece 22 by an automatic transfer device (not shown). That is, first, when the automatic transfer device carries the workpiece 22 into the reaction chamber 13, the lid driving mechanism raises the lid 115 until the lower end of the lid 115 is at substantially the same height as the upper end of the magazine 15. Let When the carry-in of the workpiece 22 is completed, the lid driving mechanism lowers the lid 115 and couples the lid 115 to the bottom 116 by a predetermined coupling means. In this state, the plasma surface treatment as described above is performed. After the plasma surface treatment is completed, the lid driving mechanism raises the lid 115 again to the height, and the automatic transfer device carries the workpiece 22 out of the reaction chamber 13.
[0025]
In the processing unit 11A as described above, by lifting the lid 115, the workpiece 22 can be smoothly carried in and out in one direction (for example, from left to right in FIG. 5). As a result of simplifying the transfer path of the workpiece 22 as described above, it is possible to simplify the configuration of the automatic transfer apparatus, and as a result, the manufacturing cost of the entire plasma surface treatment apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a plasma surface treatment apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view of a magazine.
FIG. 3 is a diagram showing a configuration of a processing unit and a configuration of an electric system related to plasma surface treatment.
FIG. 4 is a graph showing experimental results of examining the relationship between the setting of A and B dimensions and the occurrence of plasma discharge.
FIG. 5 is a view showing a modification of the processing unit.
FIG. 6 is a view for explaining the principle of a reactive ion etching mode.
FIG. 7 is a view for explaining the principle of a plasma etching mode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Plasma surface treatment apparatus 11, 11A ... Processing unit 12 ... Control unit 13 ... Reaction chamber 14, 62 ... High frequency electrode (RF electrode)
DESCRIPTION OF SYMBOLS 15 ... Magazine 151 ... Outer frame 152 ... Shelf board 153 ... Rail 20, 63 ... Ground electrode 22, 65 ... To-be-processed object 61 ... High frequency power supply (RF power supply)

Claims (3)

a) High frequency power supply,
b) a magazine including a plurality of shelves made of a conductive material for placing an object to be processed and an outer frame that hierarchically supports the shelves;
c) a reaction chamber that can be sealed with the magazine stored therein;
d) electrical connection means for electrically connecting the shelf of the magazine housed in the reaction chamber to the high frequency power source;
e) a ground electrode installed so as to cover the ceiling and side surfaces of the reaction chamber;
A plasma cleaning apparatus comprising: The plasma cleaning apparatus according to claim 1, wherein the magazine is removable from the reaction chamber. The plasma cleaning apparatus according to claim 1, wherein the shelf plate is removable from the outer frame.

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